The present invention relates generally to industrial printers and specifically to printing heads and printing arrays.
Industrial ink jet printer heads are generally constructed in either a vector or a matrix configuration. As is described in their respective names, vector printer heads include an array of ink jet nozzles arranged in a row or vector configuration, while matrix printers include a bi-dimensional array of ink jet nozzles arranged in a matrix.
One of the factors influencing the choice of printer head configurations is the desired line quality, which is defined by the number of printed dots per inch (dpi). The typical industrial standard for line quality is 600 dpi; however, this factor may increase or decrease depending on the printer capability and consumer requirements.
An additional factor influencing printer head configuration is physical mechanical restraints. The ink jet chamber is relatively large, much larger than the ink dot that it produces, and the industry engages in a perpetual search for improved ways to squeeze more ink jet nozzles into a smaller and smaller area by reducing the chamber size. U.S. Pat. No. 5,777,637 describes one such nozzle arrangement.
Reference is now made to FIGS. 1 and 2, which illustrate prior art vector printing heads and methods.
FIGS. 1A and 1B are schematic diagrams of an ink jet nozzle configuration of a page wide printing head 10 and a sheet of paper 12, and a sample of printing produced with head 10, respectively. For purposes of clarity, the latitudinal axis of paper 12 has been marked Y and the longitudinal axis has been marked X.
Head 10 comprises a row of nozzles 14 positioned along the Y-axis, which operate and eject ink in a manner known in the art for ink jet printing nozzles. For purposes of clarity, FIG. 1A illustrates a limited number of nozzles 14; however, the quantity of nozzles 14 and the distance between them may vary from printer to printer depending on the desired dpi and the width of the paper 12.
As illustrated in FIG. 1A, head 10 is laterally positioned above paper 12, and remains static while paper 12 moves in a longitudinal direction, marked by arrow 13, underneath the head.
FIG. 1B is an illustration of a printing sample produced by head 10. A vertical line 16 is comprised of a continuity of ink dots 17, as is known in the art and the thickness and quality of line 16 is determined by the printed dot size, dot ejection frequency and paper advance speed. A width W is the distance between line 16 and a line 18 and is determined by the distance between nozzles 14.
Illustrated in FIGS. 2A and 2B is an additional example of a vector-printing head 20. Similar elements from FIGS. 1A and 1B are identified by similar numbers and letters.
Similar to head 10, head 20 is positioned over paper 12, and comprises a row of nozzles 14. In contrast to head 10, which comprised a page wide row of nozzles 14 on the Y-axis, head 20 comprises a row of nozzles 14 positioned on the X-axis.
Head 20 is laterally positioned along the X-axis of paper 12 and, in a process well known in the art, transverses the Y-axis of paper 12 from side M to side N, thus printing on the section of paper 12 which falls underneath the head""s path. Paper 12 then increments the printed portion of the paper forward in the direction marked by arrow 13, and head 20 transverses paper 12 again, returning from side N to side M. The process of head transversal and paper incrementation is repeated until printing is completed for paper 12. The path of print coverage on the page is marked by dotted line 15.
FIG. 2B is an illustration of the printing produced by head 20 and shows a horizontal line 16 comprised of a continuity of dots 17, a horizontal line 18 also comprising dots 17, and a width W between two lines 16 and 18. Similar to head 10, lines 16 and 18, are determined by the printed dot quality and dpi produced by head 20, and distance W is determined by the distance between nozzles 14.
To overcome the physical limitations of inter-nozzle row width W, prior-art printing heads use the staggered nozzle construction as shown in FIG. 3.
Head 30 comprises a plurality of nozzles 14 arranged in a staggered array having parallel angled rows, referenced 38 and 40, and parallel columns, referenced A, B and C. Head 30 is not restricted to any specific array pattern and may comprise one, two or more angled rows of nozzles 14, depending on the application
For purposes of clarity, the uppermost nozzle 14 in angled row 38 is labeled 38a, the second uppermost nozzle 14 in column 38 is labeled 38b, and so on. The numbering for row 40 is similar to that of column 38; the uppermost nozzle in column 40 is labeled 40a, the second uppermost nozzle 14 is labeled 40b, and so on. Similar labeling is applicable for all columns and rows in head 30.
The rows of nozzles in head 30 are not aligned directly parallel on the Y-axis. Each of the rows 38 and 40 are offset at an angle from the Y-axis. The angle xcex8 is flexible and is determined by the desired print quality, as will be explained hereafter.
Thus, in the example shown, nozzle 38b is offset a distance W with respect to nozzle 38a, in the X direction and similarly nozzle 38c is offset a distance W with respect to nozzle 38b
The angling of the rows produces an array of nozzles 14, which are offset or angled or staggered with respect to the Y-axis. While the shortest physical distance between adjacent nozzles 14, measured on the Y-axes, is D, the distance between adjacent nozzles measured on the X-axes is W. The staggering of nozzles results in W less than  less than D, depending on the choice of angle xcex8.
If more than one angled row 38 is used, the spacing B in the X direction, between the rows 38 and 40 will be such that the last nozzle 38j in row 38 will be spaced from the first nozzle 40a at a distance W measured on the X-axis.
The printing produced by head 30, moving in the Y direction, as shown by arrow 32, is illustrated by horizontal parallel lines 52a, 52b, 52c to 52j, part of nozzle row 38, and lines 54a, 54b, 54j part of nozzle row 40. Lines 52, 54 are formed by a continuity of ink dots 17.
The structure of staggered nozzle array can achieve for example a printing line resolution of 200 dpi in the X direction by defining W=1/200xe2x80x3.
It should be noted that by a proper choice of angle xcex8, the physical distance between adjacent nozzles D is about 1.5 to 2.0 mm.
The head 30 is useful for printing at 200 dpi only if the head (or sheet of paper) moves in the direction 32, moving the same head 30 in the Y-direction will result in a much inferior dpi number.
This limitation is problematic, where the flexibility of moving the printing head at high dpi resolution in both X, Y directions is preferred.
It is an object of the present invention to provide a printing head that prints to a high resolution on both the latitudinal and longitudinal axes.
It is an additional object of the present invention to provide a printing head that is interchangeable between printers.
The present invention is a bi-axial staggered matrix-printing head.
There is thus provided in accordance with a preferred embodiment of the present invention, a printing head having a bi-axial nozzle array. The bi-axial nozzle array includes a plurality of nozzles arranged in a two-dimensional staggered array configuration, whereby the printing head is capable of printing along first and second axes, the first axis being perpendicular to the second axis.
Furthermore, in accordance with a preferred embodiment of the present invention the staggered array configuration includes a plurality of rows and plurality of columns, the plurality of columns being offset at an angle xcex1 from the first axis and the plurality of rows being offset at an angle xcex2 from the second axis.
The angles xcex1 and xcex2 are determined by the dpi (dots per inch) resolution required and the distance between adjacent nozzles.
Furthermore, in accordance with a preferred embodiment of the present invention the staggered array configuration includes a plurality of nozzles arranged in a honeycomb configuration. The plurality of nozzles is arranged such that any three nozzles form an equilateral triangle.
There is also provided in accordance with a preferred embodiment of the present invention, a biaxial printing system for printing along first and second axes, the first axis being perpendicular to the second axis. The system includes at least one printing head, each of the at least one printing head having a bi-axial nozzle array, the bi-axial nozzle array includes a plurality of nozzles arranged in a two-dimensional staggered array configuration, control means coupled to the at least one printing head for controlling the ejection of ink from each of the plurality of nozzles and a substrate for receiving the ejected ink.
Furthermore, in accordance with a preferred embodiment of the present invention, the system further includes first movement means coupled to the control means for controlled movement of the at least one printing head.
Furthermore, in accordance with a preferred embodiment of the present invention the controlled ejection of ink is synchronized with the first movement means.
Furthermore, in accordance with a preferred embodiment of the present invention the system further includes second movement means coupled to the control means for controlled movement of the substrate. The movement means includes stepping motors and encoders. The controlled ejection of ink is synchronized with the second movement means.
Finally there is also provided in accordance with a preferred embodiment of the present invention, a method for biaxial printing along first and second axes, wherein the first axis being perpendicular to the second axis. The method includes the steps of:
configuring at least one printing head, each of the printing heads having a bi-axial nozzle array, the bi-axial nozzle array including a plurality of nozzles arranged in a two-dimensional staggered array configuration;
controlling the movement of the printing head relative to a substrate;
controlling the ejection of material from the printing head onto the substrate.
Furthermore, in accordance with a preferred embodiment of the present invention the configuration step includes offsetting a plurality of rows of nozzles at an angle xcex2 from the second axis and offsetting a plurality of columns of columns at an angle xcex1 from the first axis. The angles xcex1 and xcex2 are determined by the dpi (dots per inch) resolution required and the distance between adjacent nozzles.